Expression of heterologous DNA sequences in a plant host is dependent upon the presence of operably linked regulatory elements that are functional within the plant host. Choice of the regulatory element will determine when and where within the organism the heterologous DNA sequence is expressed. Where continuous expression is desired throughout the cells of a plant, and/or throughout development, constitutive promoters are utilized. In contrast, where gene expression in response to a stimulus is desired, inducible promoters are the regulatory element of choice. Where expression in specific tissues or organs is desired, tissue-specific or tissue-preferred promoters may be used. That is, they may drive expression exclusively or preferentially in specific tissues or organs. Such promoters may be temporally constitutive or inducible. In any case, additional regulatory sequences upstream and/or downstream from a core promoter sequence may be included in expression constructs of transformation vectors to bring about varying levels of expression of heterologous nucleotide sequences in a transgenic plant.
As this field develops and more genes become accessible, a greater need exists for plants transformed with multiple genes. These multiple exogenous genes typically need to be controlled by separate regulatory sequences. Further, some genes should be regulated constitutively whereas other genes should be expressed at certain developmental stages or locations in the transgenic organism. Accordingly, a variety of regulatory sequences having diverse effects is needed.
Multiple regulatory sequences are also needed in order to avoid undesirable molecular interactions which can result from using the same regulatory sequence to control more than one gene.
Transgenic modulation of early sensing and signaling genes involved in abiotic stress responses requires expression of the transgenes early upon exposure to the stress and at a moderate level. Also, expression of such transgenes needs to be turned off at later stages of stress exposure so as to avoid the continued induction of downstream targets, a scenario which can easily lead to yield penalty. The current invention provides a regulatory sequence which can be used for early expression and tight modulation of signaling and sensing genes, for transgenic modulation of plant stress tolerance.
The inventor herein discloses the isolation and characterization of a promoter associated with a stress-related transcription factor which can serve as a regulatory element for expression of isolated nucleotide sequences of interest, thereby impacting various traits in plants. Alternatively or additionally, the promoter may be used to drive scorable markers.